In theory, you should be able to use 135% of the normal drop count of ferric (27/20 ~ 135%) to the standard metal salt drop count and deal with the additional volume of water in the coating solution by drying the coated paper a little longer. So if you normally use 10 FO and 10 Pd metal solution, use 13-14 FO and 10 Pd metal solution. The water is just a carrier to get the chemicals to saturate the paper fibers, and it should be mostly dry once the paper reaches ambient humidity.

On the other hand, ferric is ridiculously cheap compared to the metal salt, so why not just buy some more ferric oxalate and avoid the dropper count math?

Thanks Clay, it's not an economic decision but rather a time crunch decision to get this done this weekend and into the mail. All I have at the moment is a kallitype mix. I appreciate the math you provided. Thanks
regards
eRik